For example, as a technology for allowing outdoor natural light (sunlight) to efficiently travel indoors through a window glass pane, it is proposed that a daylighting film (daylighting member) is used (for example, refer to PTL 1).
The daylighting film results from forming multiple bodies (protrusion portions) in the shape of a prism on one surface of a film (base) that has optical transparency. By being attached to a window glass pane, the daylighting film radiates light towards an indoor ceiling, a side wall, or a floor while changing a propagation direction of light that is incident on the window glass pane, using the bodies in the shape of a prism.
Furthermore, because the light that is directed towards the ceiling reflects off the ceiling and radiates the inside of a room, the light substitutes illumination light. Therefore, in a case where the daylighting film that functions in this manner is used, an energy saving effect can be expected in which lighting fixtures in a building consumes less energy during the daytime.